1. Field of the Invention
The invention relates to a material processing plant comprising a first screw-type machine which is provided with a first casing, at least one first casing bore having a first axis, a first screw shaft disposed in the at least one first casing bore, a first feeding area for material to be processed, with said first feeding area projecting into the first casing bore at a first end of the first casing, a first discharge area disposed at a second end of the first casing, and a column supporting the first casing in the area of the first discharge zone, a second screw-type machine which is provided with a second casing disposed below the first casing, at least one second casing bore having a second axis, a second screw shaft disposed in the second casing bore, a second feeding area projecting into the second casing bore at a first end of the second casing, and a second discharge area disposed at a second end of the second casing, and a pipe elbow which connects the first discharge area to the second feeding area, is connected to the first screw-type machine by means of an elongation compensation device, and is connected to the second casing.
2. Background Art
In particular in the processing of plastics, it is often reasonable to provide two successive extruders, each of which performing individual processing steps. For example, when plastic material is used in the form of powder, inlet and melting of the powder can take place in a first extruder. Homogenizing and pressure build-up then takes place in a second, downstream extruder. Such successive arrangements of several extruders are known for example from EP 1 005 411 B1, U.S. Pat. Nos. 3,261,056 A, 3,860,220 A, and US 2007/0104814 A1. Most plants of the generic type known from literature and practice face problems resulting from high thermal expansion when heating up during start-up which may lead to considerable stress in the entire system.
Therefore, it is the object of the invention to develop a plant of the generic type in a way to prevent damages to the plant due to thermal elongation and expansion.
This object is attained in accordance with the invention by an expansion compensation device being provided between the column and the first casing.
According to the invention, it is thus provided, on the one hand, an elongation compensation device between the first extruder and the pipe elbow and, on the other hand, an expansion compensation device between the support adjoining the discharge area of the first extruder and the casing of said support. Compensation of expansion of the second extruder thus occurs between the casing of the first extruder and said support.
According to the embodiment of a plant wherein the expansion compensation device is configured as a slide bearing provided with a sliding surface which slopes up towards the axis in the first direction of flow, compensation of thermal expansions of the second casing of the second extruder occurs in a given, fixed relation to the elongation of the first casing of the first extruder, said relation being obtained empirically or by means of calculation.
A plant wherein the sliding surface is formed between two wedges of which a lower wedge is connected to the columns and an upper wedge is connected to the first casing, and a plant wherein the sliding surface forms an angle (α) with the first axis, whereby 0.15≦tangent α≦0.25, and in particular tangent α≈0.24, specify advantageous embodiments thereof.
A plant wherein the elongation compensation device is configured as a sliding sleeve specifies an advantageous embodiment of the elongation compensation device.
Further advantages, features and details of the invention will become apparent from the ensuing description of an exemplified embodiment when taken in conjunction with the drawing.